topic FlexCAN Timestamp support in S32K

FlexCAN Timestamp support

anakha — Fri, 05 Jul 2024 10:46:17 GMT

Hi,

I try to calculate CAN Rx message period by using timestamp but it is 16 bit and overflow for higher periods.

for testing, I am sending single CAN message for 100 times (to check fluctuation).

the measurements are like below:

Rx Period (ms)	Measured timestamp (average)
10	5000
20	10600
50	25000
100	50000
200	34470 ( + 65535(overflow) = 100000)
1000	41200
2000	17000
1	573 (this fluctuate between 125 and 1000)

The baudrate is 500 kbps and FlexCAN runs at 80 Mhz.

How can 500 is approximately refers to 1ms?
It seems there is a correlation but timestamp is 16bit and only counts to 65535. So, it overflows at 200ms for example. How can I understand if it overflows and how many times?
How can I activate HR timestamp as seen at below? I am using RTD 3.0.0 with S32DS 3.5

Is there a way to change CTRL2?

thanks in advance.

Re: FlexCAN Timestamp support

Senlent — Tue, 09 Jul 2024 06:42:54 GMT

Hi@erinc

I am working on your question.

It will take some time because there are fewer questions about FlexCAN Timestamp.

I need some time to do some testing.

Re: FlexCAN Timestamp support

Senlent — Tue, 09 Jul 2024 10:18:20 GMT

Hi@erinc

Q1.How can 500 is approximately refers to 1ms?

I think you have misunderstood. This timestamp should be the interval between the start or end of each frame, not the time it takes for a frame to be transmitted.

Q2.It seems there is a correlation but timestamp is 16bit and only counts to 65535. So, it overflows at 200ms for example. How can I understand if it overflows and how many times?

Yes, the default is the Free running 16-bit timer, which has no overflow flag(i didn't see), but you can set CRTL1[TSYN] = 1, so that the timer will automatically reset after receivied Frame.

Q3.How can I activate HR timestamp as seen at below? I am using RTD 3.0.0 with S32DS 3.5

a.You need to enable the following options:

b.You need to configure Stm for HR timestamp.(ps,:you can refer to "Stm_Gpt_Example_S32k344")

c.Read HR timestamp, for example:

temp = (uint32)IP_CAN_0->HR_TIME_STAMP[mb_idx];

Also,You can enable the interrupt of Stm and record the number of overflows of Stm